1. Field of the Invention
The invention concerns a rotor blade fastening arrangement in the drum rotor of an axial flow turbomachine, in which the roots of the blades are fastened in rows in peripheral blade grooves with support indentations at the side.
2. Discussion of Background
Such blade fastening arrangements are usually found in compressor and turbine rotors. During each rotation of the rotor, the peripheral blade grooves alter their axial dimension due to rotor bending and due to the amplitude of the bending vibrations. The dimensional change takes place with an amplitude which depends on the particular design. If the amplitude exceeds a certain magnitude, damage due to frictional fatigue can occur on the blade roots or on the turned recesses of the rotor. The corresponding parts of the first turbomachine stage in multi-stage machines are particularly endangered because there is no mutual relief provided by adjacent blade grooves. In consequence, noticeably larger relative displacement amplitudes occur in this first blade groove compared with those in the subsequent blade grooves. This matter is explained in FIGS. 2 and 3 which are described later.
In addition, strongly asymmetrical displacements occur in the first blade groove during changes in temperature, on starting, in the case of load change or of operational fluctuations. These displacements lead to excessive local surface pressures in the blade root support indentations of the first rotor row.
Finally, problems with the simultaneous contact and support of all the participating surfaces occur due to manufacturing tolerances in the case of mechanical inverted T root blade fastening arrangements which are loaded by centrifugal forces in the radial direction and by fluid forces in the axial and peripheral directions and in which the forces are transmitted to the rotor via two or more indentations.